The present invention concerns seating units having a reclineable back, and more particularly concerns seating units having a reclineable back and a forwardly movable/tiltable seat that moves with a synchronous movement as the back is reclined.
Manufacturers are becoming increasingly aware that adequate lumbar support is important to prevent lower back discomfort and distress in workers who are seated for long periods. A problem is that the spinal shape and body shape of workers vary tremendously, such that it is not possible to satisfy all workers with the same shape. Further, the desired level of firmness or force of support in the lumbar area is different for each person and may vary as a seated user performs different tasks and/or reclines in the chair and/or becomes fatigued. In fact, a static lumbar support is undesirable. Instead, it is desirable to provide different lumbar shapes and levels of support over a work day. Merely providing a particular shape or an adjustable lumbar support is not enough since seated users are constantly changing their position in the chair. Instead, the chair back must move and flex in a sympathetic manner that mirrors the movement of a human spine and lower back while providing good postural support in all body positions. Accordingly, an adjustable lumbar system is desired that is constructed to widely vary the shape and force of lumbar support. At the same time, the adjustable lumbar system must be simple and easy to operate, easily reached while seated, mechanically non-complex and low cost, and aesthetically/visually pleasing. Preferably, adjustment of the shape and/or force in the lumbar area should not result in wrinkles in the fabric of the chair, nor unacceptable loose/saggy patches in the fabric, even while the range of shape and force adjustment is increased.
A synchrotilt chair is described in U.S. Pat. No. 5,050,931 (to Knoblock) having a base assembly with a control, a reclineable back pivoted to the control, and a seat operably mounted to the back and control for synchronous motion as the back is reclined. This prior art chair incorporates a semi-rigid flexible shell that, in combination with the chair support structure, provides a highly-controlled postural support during the body movements associated with tasks/work (e.g., when the back is in an upright position) and during the body movements associated with recline/relaxation (e.g., when the chair is in a reclined position). This prior art chair moves a seated user""s upper body away from the user""s work surface as the user reclines, thus providing the user with more area to stretch. In fact, moving around in a chair and not staying in a single static position is important to good back health in workers whose jobs require a lot of sitting. However, users often want to remain close to their work surface and want to continue to work at the work surface, even while reclining and relaxing their body and while having continued good postural support.
Modern customers and chair purchasers also demand a wide variety of chair options and features, and a number of options and features are often designed into chair seats. However, improvement in seats is desired so that a seated user""s weight is adequately supported on the chair seat, but simultaneously so that the thigh area of a seated user is comfortably, adjustably supported in a manner that adequately allows for major differences in the shape and size of a seated user""s buttocks and thighs. Additionally, it is important that such options and features be incorporated into the chair construction in a way that minimizes the number of parts and maximizes the use of common parts among different options, maximizes efficiencies of manufacturing and assembling, maximizes ease of adjustment and the logicalness of adjustment control positioning, and yet that results in a visually pleasing design.
Accordingly, a chair construction solving the aforementioned problems is desired.
In one aspect on the present invention, a seating unit includes a base assembly having a seat-supporting structure, a seat supported on the base assembly, and a back frame pivoted to the base assembly for movement between upright and reclined positions. A compliant back is connected to the back frame in at least one top connection and to one of the back frame and the seat at bottom connections vertically spaced from the at least one top connection. The bottom connections are located proximate a rear of the seat and in front of a bottom of the compliant back so that the bottom connections define an axis that is adapted to be generally aligned with an area associated with a seated user""s hip bone and lower spine. The compliant back is flexible so that the compliant back undergoes controlled flexure between the top and bottom connections upon flexure of a seated user""s back. The seat has a front portion slidably supported on the seat-supporting structure of the base assembly and a rear portion pivotably connected to the back frame so that the seat moves forwardly in a synchronized motion with the back frame during recline of the back frame.
In another aspect on the present invention, a seating unit includes a base assembly, and a back frame pivoted to the base assembly for movement between upright and reclined positions. A compliant back is operably attached to the back frame at a top connection and operably attached to the back frame at bottom connections. The compliant back includes a forwardly-extending flange generally located along its lower edge forming an axis of rotation at the bottom connections. The axis is located proximate a rear section of the seat and in front of the compliant back. The compliant back includes a thoracic portion, a pelvic portion, and a flexible lumbar portion constructed so that when a seated user flexes his/her lower back rearwardly, a pelvic portion of the compliant back moves pivotally downwardly and rearwardly about the axis, the lumbar portion of the compliant back flexibly moves generally rearwardly to form a more planar arrangement with the pelvic portion, and a thoracic portion of the back pivots about the top connection. By this arrangement, the compliant back, in combination with the back frame and base assembly, is adapted to provide postural support for a seated user""s back that is comfortable and yet posturally supports significant flexing and moving of the seated user""s torso and spine.
In a seating unit having a base, a seat, a back frame rotatably attached to the base, and a first energy mechanism operably connected to the back frame and the base for biasing the back frame toward an upright position, an inventive improvement includes a compliant back that is flexibly bendable to define different curvilinear shapes for sympathetically supporting a seated user""s back, and a belt bracket with forwardly-extending flanges pivotally connecting the compliant back to the back frame at a first connection. The compliant back includes a second connection pivotally connecting the compliant back to the back frame at a second location spaced vertically from the first connection, such that the compliant back is constrained to move over a range limited by the first and second connections. A second energy mechanism includes a force generating mechanism located generally at one of the first and second connections and constructed to bias the bracket and so as to bias a lumbar portion of the compliant back forward with respect to the seating unit.
In another aspect on the present invention, a seating unit construction includes a base assembly, a seat, and a back frame pivoted to the base assembly for movement between upright and reclined positions. A compliant back is pivoted to the back frame at a fixed top connection and includes forwardly-extending flanges pivoted to one of the back frame, the seat, and the base assembly at bottom connections. The bottom connections are spaced forwardly from a lower front central surface of the compliant back, so that, upon flexure of a seated user""s spine and lower back, the compliant back is adapted to flex sympathetically and follow flexure of the seated user""s back and spine.
In another aspect on the present invention, a seating unit includes a base assembly, a seat, and an inverted U-shaped back frame having an intermediate top section and a pair of configured end sections pivoted to the base assembly, a T-shaped top connector protruding from the top section and a pair of bottom connectors in the configured end sections. A compliant back includes a top recess configured to receive and frictionally engage the top connector, and further includes a belt bracket along a lower edge with opposing flanges that extend forwardly a distance for connection to the bottom connectors. A connecting mechanism pivotally connects the opposing flanges to the bottom connectors at a location proximate a rear of the seat.
In another aspect on the present invention, a back construction for a seating unit includes a back frame, and a compliant back having a forwardly-protruding lumbar support section that is characteristically flexible and bendable, such that the compliant back can be flexed to a plurality of different convex shapes. Top and bottom connections pivotally connect the compliant back to the back frame. An adjustable force-generating mechanism is operably attached to at least one of the compliant back and the back frame. The force-generating mechanism is constructed to provide an adjustable biasing force that adjustably biases the lumbar support section forwardly for optimal lumbar support for a seated user""s back, but the force-generating mechanism characteristically provides the biasing force without forcing a shape change in the compliant back.
In another aspect on the present invention, a back construction for a seating unit includes a back frame, and a compliant back having a forwardly-protruding lumbar support section that is flexibly movable to a plurality of different convex shapes, with each shape being adapted to provide postural and comfortable support to a back of a seated user. Top and bottom connections pivotally connect the compliant back to the back frame. An adjustable torsional force-generating mechanism is operably attached to one or both of the compliant back and the back frame to bias the lumbar section forwardly for optimal lumbar support for the seated user""s back. The torsional force-generating mechanism is operably mounted at the bottom connection to the back frame and the compliant back.
In another aspect on the present invention, a seating unit includes a base assembly having a control housing having an energy source therein, a seat on the base assembly, and a back support. The back support is operably interconnected to the energy source for movement between an upright position and a reclined position. The back support includes a back frame and a back shell. The back shell includes a resiliently flexible polymeric sheet shaped to and adapted to support a back of a seated user, with a semi-rigid lower area disposed generally in a pelvic area on the seating unit, a flexible central area disposed above the lower area and generally in a lumbar area on the seating unit, and a semi-rigid upper area disposed above the central area in a thoracic area on the seating unit. The back frame has a first attachment coupling the upper area of the back shell to the back frame, and a plurality of pivotal second attachments for pivotally coupling the lower area of the back shell to the back frame. The second attachments constrains movement of the lower area to force flexure to occur in a controlled sympathetic manner in the lumbar area in order to adapt the back support to assure continuous and comfortable support of the seated user""s spine in the lumbar area during flexure of the seated user""s spine while seated. The central area of the back shell includes a plurality of vertically spaced apart slots in the sheet extending generally horizontally across a portion of the central area of the back support. The slots terminate prior to the perimeter edge of the sheet. By this arrangement, the slots define a plurality of elongated horizontal resilient straps in the central area, each of the straps being dimensioned and adapted to provide resilient support for the seated user when sitting on the seating unit. The lower area of the back shell includes a reinforcement having forward extending flanges pivotally coupled to the second attachments of the back frame. The reinforcement and pivotal attachment are adapted to provide movable firm support for at least a portion of the pelvic area of the seated user.
In another aspect on the present invention, a seating unit includes a base assembly having a control housing having an energy source therein, a seat on the base assembly, and a back support operably interconnected to the energy source for movement between an upright position and a reclined position. The back support includes a back frame and a back shell. The back shell includes a resiliently flexible polymeric sheet shaped to and adapted to support a back of a seated user, with a semi-rigid lower area disposed generally in a pelvic area on the seating unit, a flexible central area disposed above the lower area and generally in a lumbar area on the seating unit, and a semi-rigid upper area disposed above the central area in a thoracic area on the seating unit. The back frame has a first attachment coupling the upper area of the back shell to the back frame, and a plurality of pivotal second attachments for pivotally coupling the lower area of the back shell to the back frame. The second attachments constrain movement of the lower area to force flexure to occur in a controlled sympathetic manner in the lumbar area in order to adapt the back support to assure continuous and comfortable support of the seated user""s spine in the lumbar area during flexure of the seated user""s spine while seated. The central area of the back shell includes a plurality of vertically spaced apart slots in the sheet extending generally horizontally across a portion of the central area of the back support. The slots terminate prior to the perimeter edge of the sheet. By this arrangement, the slots define a plurality of elongated horizontal resilient straps in the central area, each of the straps being adapted and dimensioned so as to provide resilient support for the seated user when sitting on the seating unit. The lower area of the back shell includes a reinforcement having forward extending flanges pivotally coupled to the second attachments of the back frame, the reinforcement and pivotal attachment being adapted to provide movable firm support for at least a portion of the pelvic area of the seated user. The pivotal second attachments pivotally couple the lower area of the back shell to the back frame and include a biasing device that biases the central area of the back shell in a forward direction.
In another aspect on the present invention, a seating unit includes a base assembly having a control housing having an energy source therein, a seat on the base assembly, and a back support. The back support is operably interconnected to the energy source for movement between an upright position and a reclined position. The back support includes a back frame and a back shell. The back shell includes a resiliently flexible polymeric sheet shaped to and adapted to support a back of a seated user, with a semi-rigid lower area disposed generally in a pelvic area on the seating unit, a flexible central area disposed above the lower area and generally in a lumbar area on the seating unit, and a semi-rigid upper area disposed above the central area and in a thoracic area on the seating unit. The back frame has a first attachment coupling the upper area of the back shell to the back frame, and a plurality of pivotal second attachments for pivotally coupling the lower area of the back shell to the back frame. The second attachments constrain movement of the lower area to force flexure to occur in a controlled sympathetic manner in the lumbar area in order to adapt the back support to assure continuous and comfortable support of the seated user""s spine in the lumbar area during flexure of the seated user""s spine while seated. The lower area of the back shell includes forward extending flanges forming an axis of rotation at the pivotal second attachments of the back frame. The axis of rotation is located at or rearward of a rear of the seat so that the axis is generally adapted for location proximate a seated user""s pelvic bone so that when the seated user flexes his/her lower back rearwardly, the lower portion of the back shell moves downwardly and rearwardly, and the central portion of the back shell flexes generally rearwardly to form a more planar arrangement with the lower portion.
In another aspect on the present invention, a seating unit includes a base assembly having a control housing having an energy source therein, a seat on the base assembly, and a back support operably interconnected to the energy source for movement between an upright position and a reclined position. The back support includes a back frame and a back shell. The back shell includes a resiliently flexible polymeric sheet shaped to and adapted to support a back of a seated user, with a semi-rigid lower area disposed generally in a pelvic area on the seating unit, a flexible central area disposed above the lower area and generally in a lumbar area on the seating unit, and a semi-rigid upper area disposed above the central area and generally in a thoracic area on the seating unit. The frame has first attachments coupling the upper area of the back shell to the back frame, and a plurality of pivotal second attachments for pivotally coupling the lower area of the back shell to the back frame. The second attachments constrain movement of the lower area to force flexure to occur in a controlled sympathetic manner in the lumbar area in order to adapt the back support to assure continuous and comfortable support of the seated user""s spine in the lumbar area during flexure of the seated user""s spine while seated, the back frame defining a curvilinear arch.
In another aspect on the present invention, a seating unit including a base assembly having a control housing having an energy source therein, and a back assembly movably supported on the back assembly. The back assembly includes a back support operably interconnected to the energy source. The back support includes a back frame and a back shell connected to the back frame by at least one connection. The back shell includes a resiliently flexible polymeric sheet adapted to support a back of a seated user. The sheet includes a lower area disposed generally in a pelvic area on the seating unit, a central area disposed above the lower area and generally in a lumbar area on the seating unit, and an upper area disposed above the central area and generally in a thoracic area on the seating unit. A cushion is provided on a forward face of the back shell. A vertically adjustable lumbar support is located in front of the back shell. The lumbar support is movably supported on the back support and configured for vertical adjustment to change a shape of a front surface of the back in the lumbar area. The vertically adjustable lumbar support includes laterally extending handles constructed to engage and follow configured non-parallel opposing perimeter edges of the back shell and constructed to slidably engage the vertically adjustable lumbar support to permit the handles to adjust laterally in and out to follow the perimeter edges.
In another aspect on the present invention, a seating unit includes a base assembly, a seat supported on the base assembly, and a back frame pivoted to the base assembly for movement between upright and reclined positions. A compliant back is pivotally connected to the back frame in at least one top connection and pivotally connected to one of the back frame and the seat at bottom connections vertically spaced from the at least one top connection. The bottom connections are located proximate a rear of the seat and in front of a bottom of the compliant back so that the bottom connections define an axis at a rear of the seat that is adapted to be generally aligned with a seated user""s hip bone. The compliant back has a stiff thoracic section and a stiff pelvic section. The lumbar section is characteristically flexible in a horizontal direction, such that the compliant back can be easily flexed to provide different shapes for optimal lumbar support. However, at the same time, the lumbar section is substantially incompressible in directions toward the thoracic and pelvic sections so that the lumbar section causes the thoracic and pelvic sections to pivot along predetermined paths about the top and bottom connections when the lumbar section is flexed. By this arrangement, the compliant back undergoes controlled flexure between the top and bottom connections upon flexure of the lumbar section caused by flexure of a seated user""s back. The seat is operably supported on the base assembly to move in a synchronized angular motion with the back frame during recline of the back frame.
In another aspect on the present invention, a seating unit includes a base assembly, a back frame pivoted to the base assembly for movement between upright and reclined working positions, and a compliant back operably attached to the back frame at a top connection and operably attached to the back frame at bottom connections. The compliant back includes a stiff thoracic portion and a stiff pelvic portion connected by a flexible lumbar portion. The bottom connections are forward of the pelvic portion and above the seat. The top and bottom connections and thoracic, pelvic, and lumbar portions are constructed so that when a seated user flexes his/her lower back rearwardly, the pelvic portion of the compliant back moves pivotally downwardly and rearwardly, the lumbar portion of the compliant back flexibly moves generally rearwardly to form a more planar arrangement with the pelvic portion, and the thoracic portion of the back pivots about the top connection. By this arrangement, the compliant back, in combination with the back frame and base assembly, is adapted to provide postural support for a seated user""s back that is comfortable and yet posturally supports significant flexing and moving of the seated user""s torso and spine.
In another aspect on the present invention, a seating unit includes a base assembly, a seat operably supported on the base assembly, and a back frame pivoted to the base assembly for movement between upright and reclined working positions. A compliant back is operably attached to the back frame at a top connection and is operably attached to one of the seat and the back frame at bottom connections. The compliant back includes a stiff thoracic portion and a stiff pelvic portion connected by a flexible lumbar portion. The bottom connections are forward of the pelvic portion and above the seat. The top and bottom connections and the thoracic, pelvic, and lumbar portions are constructed so that when a seated user flexes his/her lower back rearwardly, the pelvic portion of the compliant back moves pivotally downwardly and rearwardly, the lumbar portion of the compliant back flexibly moves generally rearwardly to form a more planar arrangement with the pelvic portion, and the thoracic portion of the back pivots about the top connection. By this arrangement, the compliant back, in combination with the back frame and base assembly, is adapted to provide postural support for a seated user""s back that is comfortable and yet posturally supports significant flexing and moving of the seated user""s torso and spine.
These and other features and advantages of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.